The invention concerns an electroportable apparatus for setting nuts or blind rivets whose shanks rupture.
At present, apparatus for setting nuts or blind rivets whose shanks ruptures rupture, are supplied by electrical cables or pneumatic cables. Along assembly lines where several people work, there is rapidly an overlapping of wires which is undesirable for working safety.
More and more, industries are oriented toward apparatus of this type, which is portable and which imparts comfort and efficiency to work. These portable apparatuses are very bulky and highly energy consumptive. They therefore have a short charge and must often be recharged.
The state of the art can be defined by the following patents.
WO95/13887: The tool for setting rivets and self-tapping screws, comprises a movable body, terminating in a head permitting holding the rivet or the self-tapping screws so as to be driven in rotation by the electrical motor with gearing and by means of the intermediate screw which is provided with a pulling device. The tool is contained in a housing of the electroportable type, and provided with a loader-distributor of screws or self-penetrating rivets.
WO96/25258: The invention relates to a self-piercing riveting device, actuated by a motor and comprising a housing held by an operator. The housing contains a motor driving a principal pinion, connected by a transmission wheel to the cam driving a riveting mechanism, this latter being well known in the field of art to which it relates. The above mechanism is installed in an independently rotatable cylinder turning directly the riveting mechanism. When the device operates, a rotative couple is first impressed on the riveting mechanism by the transmission wheel so as to clamp the jaws about a shank until the rotation couple is minimal, necessary to burst a rivet, namely, superior to that which is required to pierce a workpiece to be machined; the transmission wheel will then cease to turn to transform it into an orbital wheel for the drive pinion. The rotatable cylinder then causes to turn and move the self-piercing rivet. Boring of the workpiece takes place until the rivet is emplaced. Increased pressure on the trigger switch brakes the rotatable cylinder, driving the rotatable coupler rearwardly on the transmission wheel to shape the rivet, after which the cam, because of maintaining the braking pressure controlled by the triggering switch, gives rise to the return by 360xc2x0 of arc, of the mechanism, so as to get rid of the shank that was used and to receive another.
EP-A-0 670 199: Apparatus for placing the female portion of a blind rivet is provided, with a traction rod, a motor, a first drive transmission to generate rotatable movement of the traction rod and which can be interrupted and a second drive transmission which has a drive portion and a driven portion and in which the driving portion can be moved over a path of movement and which has an empty space relative to the driven portion and a usable path.
FR-A-2.706.338: The invention relates to a riveting tool with a system for sucking up rivets, comprising a body which is connected to a lower portion and carrying an upper portion with a gripping assembly for the shank of the rivet that is hydraulically controlled, said gripping assembly being provided with a pincers mandril and a hydraulic jack being connected to a space above the upper portion of the pneumatic piston which is formed in the body of the tool, an air outlet under the pressure of a control valve opening into a space below the lower portion of the pneumatic piston which is guided in a cylindrical reinforcement of the lower portion of the tool, said control valve being fixed in an imperforate separation wall of the lower portion of the tool and being connected by means of a valve rod, freely guided in the longitudinal recess of the body, with a detent which is slidably mounted in a transverse guide.
There are known devices having less encumbrance. Thus, EP-A-0 527 414 provides an apparatus for blind rivets with a housing and a traction device having a gripping mechanism, which can be moved by an electric motor by means of a drive device. Such an apparatus for blind rivets must be actuated with increased comfort. To do this, the drive apparatus as a demultiplying ratio independent of the position of the traction device and giving rise to a permanent relationship between the electric motor and a traction device which ensures that the movement of the traction device takes place solely under the control of the electric motor.
Such an apparatus however does not give entire satisfaction.
First, there is proposed a constant demultiplication ratio all along the path of the traction device. An important drawback of this choice is that a maximum drive couple in the middle of the path cannot be targeted, which is to say at the moment at which the riveting requires the greatest coupling.
Moreover, the design of the apparatus according to EP-A-0 527 414 is very particular to the transmission system. The horizontal position of the motor is less ergonomic and the choice of a ball screw coaxial with the traction device to actuate it is a heavy and costly technical solution.
Moreover, it is essentially the relaxation of the trigger which controls the return of the traction device. This path control is different from that of the present invention and has the drawback of risking bad riveting if the operator too quickly releases the trigger or if he does not detect an anomaly such as wire drawing.
Finally, economy of electrical consumption is not optimal, because it can be, by tardy release of the trigger, that the traction path that is necessary and sufficient is exceeded.
The present invention seeks to overcome the drawbacks of the present art.
The apparatus according to the invention, for the setting of screws or blind rivets, is of the type comprising an electroportable body, containing an electric motor, a mandrel, drive means to maintain and pull on the nail or rivet and/or to pull, screw or unscrew the nut to be set.
The apparatus further comprises preadjustment means of the path of the mandrel, permitting, after the pre-regulated course of the mandrel, an automatic return.
The invention can take several embodiments disclosed hereafter.
The amplitude of the path of the mandrel is adjustable as a function of the size of the nut or rivet to be set.
Adjustment of the path of the mandrel is a distance adjustment.
The pre-adjustment means are constituted by a slider which moves a detector that is movable relative to a fixed detector.
The pre-selection of the rivet and/or of the nut to be set is carried out by a potentiometer which measures electronically the distance of the path of the mandrel.
The mechanical apparatus for setting blind rivets comprises an electric motor driving a ball screw, which drives by means of balls, a toothed wheel actuating a rack driving the riveting mechanism.
The electric motor is a coupled motor.
The drive means actuating the riveting mechanism are actuated by a hydraulic micro-central, the motor actuates the hydraulic micro-central, and energy transmission takes place by means of a hydraulic pump, which is an integral portion of the hydraulic micro-central.
The mandrel is adapted to position nuts and an electric motor is disposed on the working axis of the mandrel for screwing or unscrewing.
The trigger of the apparatus is the control means, the first pull actuating screwing of the second pull actuating pulling along a predetermined path with automatic return and upon releasing the trigger, the automatic unscrewing action for x turns of the motor and stopping said motor.
The trigger is connected by a branched distributor to a connection socket, itself connected to another socket, which is connected to the hydraulic circuit, which supplies point A and point B and on the other hand the piston, secured to the hollow mandrel, O-rings ensuring the sealing of the hydraulic assembly, a return spring for the hollow mandrel, the end of the hollow mandrel is disposed at the level of the recess, which gathers the nails when they are pulled, and that the end of the hollow mandrel is located at the level of the nose and of the pulling broach of the electrohydraulic riveter.
The trigger has two functions:
first, the trigger closes in a first instance the hydraulic circuit A and B,
secondly, the same trigger starts the motor, which drives the pump, for the regulated pre-established path, and that the release of the trigger by opening the hydraulic circuit, drives the return of the piston, namely of the hollow mandrel to the rear. The electric motor is positioned substantially along the vertical axis of the electroportable body and is mounted with a freedom of movement in pivoting relative to the electroportable body.
The adjustment of the path of the mandrel is a distance adjustment.
The cycle of operation of the electroportable riveter with an adjustable path can be the following.
The motor-couple is supplied by a power circuit closed by two relays which permit the circulation of current and its inversion.
The control circuit is controlled by a sequential command or a holding contact. This control is actuated by a control trigger disposed on the body of the apparatus. The current flows then into a first branch of the control circuit. This first branch is opened by a contact which symbolizes the end of path contact. The switch then swings to supply a second branch of the control circuit which controls a relay, the power current circulates in the reverse direction, the motor-couple changes as to direction of rotation and returns the drive means to the initial position.
It will thus be understood that the trigger controls the starting of the cycle but that it does not control the return by inversion of the motor-couple. The return takes place without control, by detection when the pre-regulated course is achieved.
In this way, bad riveting is avoided because, upon the systematic execution of a certain path, the anomalies such as wire drawing will be reduced, as well as sliding by wear of a jaw or else an error of punching the sheet metal to be riveted.
According to another embodiment, the drive means actuating the riveting mechanism are actuated by a hydraulic micro-center.
The motor-couple actuates the hydraulic micro-center.
The transmission of energy takes place by means of a hydraulic pump, which is an integral part of the hydraulic micro-center.
In the embodiment in which the apparatus is adapted to set nuts, the mandrel is adapted to position these nuts and an electric motor is disposed along the working axis of the mandrel to screw or unscrew them.
The trigger of the apparatus is the control means.
The first pull actuates screwing, and, the screwing terminated, pulling continues to actuate the traction on the predetermined path with an automatic return.
Upon releasing the trigger, there is an automatic unscrewing action for x turns of the motor and stopping of said motor.
In the case of low battery, a second pull gives rise to a return to zero position.
Preferred embodiments of the invention are given hereafter.
The adjustment of the path of the mandrel is a distance adjustment. There are thus detected the extreme positions of the mandrel for biasing detectors. Other adjustment means, such as counting the number of turns of the motor or from the angular position of the toothed drive wheel, can be provided.
The adjustment of the path of the rivet whose dimensions have been selected, takes place automatically by an electronic control means.
The pre-selection of the rivet and/or of the nut to be set, is carried out manually by a cursor which moves a movable detector relative to a fixed detector.
The pre-selection of the rivet and/or of the nut to be set is carried out by a potentiometer which controls electrically the distance of the path of the mandrel.
The characteristic techniques of the motor-couple are to develop maximum power for several seconds.
The characteristics can be as follows:
couple constant: 19.4 mNm/A
speed constant: 491 tr/min/V
load constant: 8.45 tr/min/mNm